切换到ASP.NET 3.5，DropDownList不记得动态添加的项目

I have a site that uses a couple DropDownLists that are databound. I was also doing the traditional if (!IsPostBack) {list.Databind();} and relied on viewstate to keep the lists filled during a post back. I recently converted the site to ASP.NET 3.5 and noticed that the lists are empty during postback (as if ViewState is disabled). I didn't explicitly disable anything, and am wondering if anyone has seen a similar change or behavior in their viewstate dependent controls.I have a site that uses a couple DropDownLists